I believe Shih Tzus are toy breeds. I don't think they have a specific "job" like a hunting dog. I have two Westie mixes, and they both definitely display some of the traits of a Westie (sniffing out everything, stubbornness). One is half poodle, and the other half Lasa Apso. We basically go on walks and play in the apartment. You could try taking yours to a dog park to use up some of the energy, or maybe arrange "playdates" with friends who have dogs? I've found now that I have two they can amuse themselves (sometimes, although they definitely prefer to be amused by me! lol)